Method of operating a wormgear drive at high energy efficiency

Abstract

This invention is directed to a method of operating a wormgear drive at high energy efficiency comprising filling an oil reservoir with a wormgear lubricant comprising an isomerized Fischer-Tropsch derived distillate fraction having a low traction coefficient and operating the wormgear drive with the filled oil reservoir at an equilibrium temperature between 20 and 225 degrees C. This invention is also directed to a process for reducing the traction coefficient of a higher-traction coefficient lubricating base oil by blending it with an isomerized Fischer-Tropsch derived distillate fraction. This invention is also directed to a wormgear lubricant comprising an isomerized Fischer-Tropsch distillate fraction and between 2 and 50 weight percent thickener.

1. A method of operating a wormgear drive at high energy efficiency, comprising:
 a. filling an oil reservoir with a wormgear lubricant comprising an isomerized Fischer-Tropsch derived distillate fraction having a traction coefficient less than or equal to 0.021, when measured at a kinematic viscosity of 15 cSt and at a slide to roll ratio of 40 percent; and 
 b. operating the wormgear drive having the filled oil reservoir at an equilibrium oil temperature in the oil reservoir between 20 and 225 degrees C. 
 
     
     
       2. The method of  claim 1  wherein the equilibrium oil temperature is between 20 and 150 degrees C. 
     
     
       3. The method of  claim 1  additionally comprising the step of draining the oil reservoir of used oil prior to filling. 
     
     
       4. The method of  claim 1  wherein the traction coefficient is less than an amount calculated by the equation: Traction Coefficient=0.009×Ln(Kinematic Viscosity in cSt)−0.001, wherein the Kinematic Viscosity during the traction coefficient measurement is between 2 and 50 cSt; and wherein the traction coefficient is measured at an average rolling speed of 3 meters per second, a slide to roll ratio of 40 percent, and a load of 20 Newtons. 
     
     
       5. The method of  claim 1  wherein the isomerized Fischer-Tropsch derived distillate fraction has a weight percent aromatics less than 0.30. 
     
     
       6. The method of  claim 5  wherein the isomerized Fischer-Tropsch derived distillate fraction has a weight percent aromatics less than 0.10. 
     
     
       7. The method of  claim 1  wherein the isomerized Fischer-Tropsch derived distillate fraction has a weight percent of molecules with cycloparaffin functionality greater than 3. 
     
     
       8. The method of  claim 7  wherein the isomerized Fischer-Tropsch derived distillate fraction has a weight percent of molecules with cycloparaffin functionality greater than 5. 
     
     
       9. The method of  claim 8  wherein the isomerized Fischer-Tropsch derived distillate fraction has a weight percent of molecules with cycloparaffin functionality greater than 10. 
     
     
       10. The method of  claim 1  wherein the isomerized Fischer-Tropsch derived distillate fraction has a kinematic viscosity at 100 degrees C. greater than 2 cSt and less than 30 cSt. 
     
     
       11. The method of  claim 10  wherein the isomerized Fischer-Tropsch derived distillate fraction has a kinematic viscosity at 100 degrees C. greater than 3 cSt and less than 10 cSt. 
     
     
       12. The method of  claim 1  wherein the isomerized Fischer-Tropsch derived distillate fraction has a ratio of pour point in degrees C. to kinematic viscosity at 100 degrees C. in cSt greater than the Base Oil Pour Factor as calculated by the following equation: 
       Base Oil Pour Factor=7.35 ×Ln(Kinematic Viscosity at  100° C.)−18. 
     
     
       13. The method of  claim 1  wherein the isomerized Fischer-Tropsch derived distillate fraction has a Free Carbon Index between 2 and 12, and additionally contains less than 12 alkyl branches per 100 carbons. 
     
     
       14. The method of  claim 13  wherein the isomerized Fischer-Tropsch derived distillate fraction has a Free Carbon Index between 3 and 10, and additionally contains less than 10 alkyl branches per 100 carbons. 
     
     
       15. The method of  claim 1  wherein the isomerized Fischer-Tropsch derived distillate fraction has an elastohydrodynamic (EHD) film thickness greater than 175 nanometers when measured at a kinematic viscosity of 15 cSt. 
     
     
       16. The method of  claim 15  wherein the EHD film thickness is greater than an amount calculated by the equation: EHD film thickness in nanometers=(10.5×Kinematic Viscosity in cSt)+20, wherein the Kinematic Viscosity during the EHD film thickness measurement is between 2 and 50 cSt; measured at an entrainment speed of 3 meters per second, a slide to roll ratio of zero percent, and a load of 20 Newtons. 
     
     
       17. The method of  claim 1  wherein the Noack volatility is less than an amount calculated by the equation: Noack Volatility=1000×(Kinematic Viscosity at 100° C. in cSt) −2.7 . 
     
     
       18. The method of  claim 1  wherein the viscosity index is greater than an amount calculated by the equation: Viscosity Index=28×Ln(Kinematic Viscosity at 100° C.)+95. 
     
     
       19. A process for reducing the traction coefficient of a higher-traction coefficient lubricating base oil having a traction coefficient greater than 0.024 when measured at a kinematic viscosity of 15 cSt and at a slide to roll ratio of 40 percent, comprising:
 a. recovering an isomerized Fischer-Tropsch derived distillate fraction having a traction coefficient less than or equal to 0.021, when measured at a kinematic viscosity of 15 cSt and at a slide to roll ratio of 40 percent; and 
 b. blending the isomerized Fischer-Tropsch derived distillate fraction with the higher-traction coefficient lubricating base oil in the proper proportion to produce a lubricating base oil blend having a traction coefficient less than the traction coefficient of the higher-traction coefficient lubricating base oil. 
 
     
     
       20. The process of  claim 19  wherein the traction coefficient of the lower-traction coefficient isomerized Fischer-Tropsch derived distillate fraction is less than an amount calculated by the equation: Traction Coefficient=0.009×Ln(Kinematic Viscosity of the lower-traction coefficient lubricating base oil in cSt)−0.001; wherein the traction coefficient is measured at an average rolling speed of 3 meters per second, a slide to roll ratio of 40 percent, and a load of 20 Newtons. 
     
     
       21. The process of  claim 19  wherein the lubricating base oil blend has a traction coefficient less than an amount calculated by the equation: traction coefficient=0.013×Ln(Kinematic Viscosity of the lubricating base oil blend in cSt)+0.001, wherein the Kinematic Viscosity of the lubricating base oil blend during the traction coefficient measurement is between 2 and 50 cSt; and wherein the traction coefficient is measured at an average rolling speed of 3 meters per second, a slide to roll ratio of 40 percent, and a load of 20 Newtons. 
     
     
       22. The process of  claim 19  wherein the higher-traction coefficient lubricating base oil is selected from the group consisting of polyalphaolefin, polyinternalolefin, petroleum derived Group I base oil, petroleum derived Group II base oil, petroleum derived Group III base oil, and mixtures thereof. 
     
     
       23. The process of  claim 22  wherein the higher-traction coefficient lubricating base oil is a petroleum derived Group II base oil. 
     
     
       24. The process of  claim 19  wherein the higher-traction coefficient lubricating base oil has a traction coefficient greater than an amount calculated by the equation: Traction coefficient=0.009×Ln(Kinematic Viscosity of the higher-traction coefficient lubricating base oil in cSt), wherein the Kinematic Viscosity of the higher-traction coefficient lubricating base oil during the traction coefficient measurement is between 2 and 50 cSt; and wherein the traction coefficient is measured at an average rolling speed of 3 meters per second, a slide to roll ratio of 40 percent, and a load of 20 Newtons. 
     
     
       25. The process of  claim 19  wherein the isomerized Fischer-Tropsch derived distillate fraction has a weight percent aromatics less than 0.30. 
     
     
       26. The process of  claim 25  wherein the isomerized Fischer-Tropsch derived distillate fraction has a weight percent of molecules with cycloparaffin functionality greater than 3 and a ratio of weight percent of molecules with monocycloparaffin functionality to weight percent of molecules with multicycloparaffin functionality greater than 15. 
     
     
       27. The process of  claim 19  wherein the isomerized Fischer-Tropsch derived distillate fraction has a Free Carbon Index between 3 and 10, and additionally contains less than 10 alkyl branches per 100 carbons. 
     
     
       28. The process of  claim 19  wherein the isomerized Fischer-Tropsch derived distillate fraction has a kinematic viscosity at 100 degrees C. greater than 2 cSt and less than 30 cSt. 
     
     
       29. The process of  claim 19  wherein the isomerized Fischer-Tropsch derived distillate fraction has a viscosity index greater than the amount calculated by the equation: Viscosity Index=28×Ln(Kinematic Viscosity at 100° C.)+95. 
     
     
       30. A wormgear lubricant comprising:
 a. an isomerized Fischer-Tropsch derived distillate fraction having:
 i. a traction coefficient less than or equal to 0.021, when measured at a kinematic viscosity of 15 cSt and at a slide to roll ratio of 40 percent; and 
 
 b. between 2 and 50 weight percent thickener selected from the group consisting of polyisobutylene, high molecular weight complex esters, butyl rubber, olefin copolymers, styrene-diene polymer, polymethacrylate, styrene ester, and mixtures thereof. 
 
     
     
       31. The wormgear lubricant of  claim 30  wherein the isomerized Fischer-Tropsch derived distillate fraction has a traction coefficient less than amount calculated by the equation: traction coefficient=0.009×Ln(Kinematic Viscosity)−0.001, wherein the Kinematic Viscosity during the traction coefficient measurement is between 2 and 50 cSt; and wherein the traction coefficient is measured at an average rolling speed of 3 meters per second, a slide to roll ratio of 40 percent, and a load of 20 Newtons. 
     
     
       32. The wormgear lubricant of  claim 30  wherein the isomerized Fischer-Tropsch derived distillate fraction is present in an amount between 10 and 93 weight percent of the total composition. 
     
     
       33. The wormgear lubricant of  claim 30  wherein the isomerized Fischer-Tropsch derived distillate fraction has a weight percent aromatics less than 0.30. 
     
     
       34. The wormgear lubricant of  claim 30  wherein the isomerized Fischer-Tropsch derived distillate fraction has:
 a. a weight percent of molecules with cycloparaffin functionality greater than 3; and 
 b. a ratio of weight percent of molecules with monocycloparaffin functionality to weight percent of molecules with multicycloparaffin functionality greater than 15. 
 
     
     
       35. The wormgear lubricant of  claim 30  wherein the isomerized Fischer-Tropsch distillate fraction has a viscosity index greater than an amount calculated by the equation: Viscosity Index=28×Ln(Kinematic Viscosity at 100° C.)+95. 
     
     
       36. The wormgear lubricant of  claim 30  additionally comprising a base oil selected from the group consisting of conventional PAO, alkylated naphthalene, polyinternalolefin, petroleum derived Group I, petroleum derived Group II, petroleum derived Group III, and mixtures thereof. 
     
     
       37. The wormgear lubricant of  claim 30  wherein the thickener is selected from the group consisting of polyisobutylene, high molecular weight complex ester, and mixtures thereof. 
     
     
       38. The wormgear lubricant of  claim 37  additionally comprising a base oil selected from the group consisting of conventional PAO, alkylated naphthalene, polyinternalolefin, petroleum derived Group I, petroleum derived Group II, petroleum derived Group III, and mixtures thereof. 
     
     
       39. The method of  claim 1  wherein the wormgear lubricant additionally comprises a thickener selected from the group consisting of polyisobutylene, high molecular weight complex esters, butyl rubber, olefin copolymers, styrene-diene polymer, polymethacrylate, and styrene ester. 
     
     
       40. The method of  claim 7  wherein the isomerized Fischer-Tropsch derived distillate fraction has a ratio of weight percent molecules with monocycloparaffin functionality to weight percent of molecules with multicycloparaffin functionality greater than 15. 
     
     
       41. The method of  claim 40  wherein the ratio of weight percent of molecules with monocycloparaffin functionality to weight percent of molecules with multicycloparaffin functionality is greater than 20. 
     
     
       42. The process of  claim 19  wherein the isomerized Fischer-Tropsch distillate fraction has a ratio of pour point in degrees C. to kinematic viscosity at 100 degrees C. in cSt greater than a Base Oil Pour Factor as calculated by the equation: Base Oil Pour Factor=7.35×Ln(Kinematic Viscosity at 100° C.)−18. 
     
     
       43. The process of  claim 19  wherein the higher-traction coefficient lubricating base oil has a traction coefficient greater than 0.030, when measured at a kinematic viscosity of 15 cSt and at a slide to roll ratio of 40 percent. 
     
     
       44. The wormgear lubricant of  claim 30  wherein the isomerized Fischer-Tropsch derived distillate fraction has a ratio of pour point in degrees C. to kinematic viscosity at 100 degrees C. in cSt greater than a Base Oil Pour Factor as calculated by the equation: Base Oil Pour Factor=7.35×Ln(Kinematic Viscosity at 100° C.)−18. 
     
     
       45. The wormgear lubricant of  claim 30  wherein the isomerized Fischer-Tropsch derived distillate fraction has a viscosity index greater than an amount calculated by the equation: Viscosity Index=28×Ln(Kinematic Viscosity at 100° C.)+95. 
     
     
       46. The wormgear lubricant of  claim 30  additionally comprising an ultra high viscosity PAO.